This week’s nuclear test by North Korea is once again testing international alliances, with U.S. Secretary of State John Kerry warning Beijing on Thursday that it must step up its efforts to force the North Korean regime to give up its nuclear program. But for China, concerns about the regime’s possible collapse likely still supercede its concerns over North Korea’s nuclear capabilities.

“This puts China in a very difficult position," noted Victor Teo, an assistant professor at the University of Hong Kong. "China is North Korea’s most important ally, since the 1950s. It is the main supplier of energy and on the ground food supply to the North Korean people.”

China is North Korea’s neighbor, and while diplomatic relations have weakened in recent years, economic ties remain strong. Trade between the two countries totaled $6.4 billion in 2014.

Trade restrictions

The United States says China could pressure North Korea by cutting energy to the country and restricting trade. China cut crude oil exports to North Korea in 2013 after an earlier nuclear test. But a wide array of international sanctions that mostly target North Korea’s military have failed to influence the regime.

North Korea has conducted four nuclear tests since 2006.

“We have to recognize that the North Korea nuclear issue is a huge challenge for everyone, and in fact it is not just China’s problem," said Wang Dong, a professor of international relations at Peking University. "China by itself cannot solve that problem.”

People watch a news report on North Korea's first hydrogen bomb test at a railroad station in Seoul on Jan. 6, 2016.

Chinese resistance

China is likely to resist public pressure from the United States to radically change its policies and trade ties with North Korea. The regime offers a strategic buffer on China’s northeastern border, and North Korea’s collapse would bring instability to a country already facing an economic slowdown, a rising number of labor protests through the country and unrest in Tibet and Xinjiang on its western border. Xiaohe Cheng is a professor at Renmin University.

“Certainly China will cooperate with the U.S., but China is not in a position to adopt the United States’ recommended proposals totally. China will offer its own proposals.”

Earlier this week, Chinese state media condemned North Korea for the nuclear test, but said China alone is not responsible for pressuring the regime.

In an editorial, the China Daily warned that Beijing "should not bear the brunt of the deadlock" between the United States and North Korea following the Korean War.